I have two lines.
I have each $X$, $Y$.
I want to find the angle between them (please mark if your method returns radians or degrees)
Aka a function $F[x, y, x_2, y_2, C_x, C_y]$ that will return their angle (at crossing point...)
While $C_x$ and $C_y$ are Cross-point $X$ and $Y$, that means they point where they touch, assuming input is OK. (in the image its the center dot)